Homework Help: Calculating weight on mars

1. Feb 16, 2005

xelda

How much would someone who has a mass 54.1 kg on Earth weigh if they were to stand on the surface of Mars? (Take RMars= 3393 km and MMars=6.45x10^23 kg.

I've been using the formula F=GmM/R^2 with the 3393km converted to meters.

(6.67 x 10^-11 Nm^2/kg^2) (54.1 kg) (6.45 x 10^23kg) / (3393000 km)^2

This gives me 202.17 N.

Isn't this the gravitational force? So if I multiplied this by the 54.1kg, wouldn't this give me the weight? I ended up with 10937.36 kg, but this doesn't seem right.

2. Feb 16, 2005

Staff: Mentor

Yes. And the gravitational force is the weight. (You're done.)
That's all meaningless. Perhaps you are confusing things with W = mg?

3. Feb 16, 2005

tony873004

gravity of mars is GM / r^2

gravity of mars = 9.81 * 0.1 / 0.5^2

9.81 is the gravitational constant if your output units are meters / second squared, and your input units are Earth masses, and Earth radii. Mars is ~ 10% of Earth's mass, and 50% of its radius.

Or you could use 6.71*10^-11 * mass of mars in kilograms * radius of mars in meters

these formulas give you acceleration. If you plug in Earth's numbers into these formulas you get 9.81, which is acceleration (g) at Earth's surface.

Now use F=ma, where F will be your weight in Newtons. Translate that into pounds.